nightly build has a 'Key Type' option for new keys

[LRvKochel]

Firstly I add my compliments for a really great piece of software - functionality is well thought out and the UI is likewise great.

I noticed in a recent nightly build there is, in the new key dialog an advanced section and in there is a Key Type pop up menu. At present ECDSA-256 s the only one.

Doe this mean that in future either key types will be available (like ED25519 or RSA)? I thought apps could only use what the SEP offered, and that is limited at present to ECDSA.

Are other key types available but Secretive is yet to support them or is it known that future hardware models will add this support?

Many thanks.

LR.

[maxgoedjen]

@LRvKochel 👀 good eye
CryptoKit offers MLDSA (post-quantum!) key support in macOS 26. It won't show up until you update, but it's in the nightly builds. It's complicated a little bit by there being virtually no server support for it yet, but there's a draft IETF for it https://datatracker.ietf.org/doc/draft-sfluhrer-ssh-mldsa/

(as an aside, Secretive does also technically support RSA keys, but only in the smartcard/yubikey context).

[LRvKochel]

Thank you. So the extra key type will be MLDSA related? The SEP still won't support Ed25519 or RSA itself?

My interest is in using a tool that has encryption/decryption functions based on the key available in an ssh agent. That tool only works with RSA and Ed25519. Its author says that ECDSA is not deterministic in a way that provides a way to predictably derive a key. So can't support it. Alas.

Nevertheless MLDSA has provided some interesting reading.

Cheers.

[maxgoedjen]

Correct – I don't anticipate it ever supporting RSA (kinda feels like that's basically a "legacy" protocol at this point, nobody really seems to recommend making new keys in it). I was definitely surprised to find them supporting a new key type at all – I had assumed the limitation was something deeper than just "we decided not to." But given that they've already implemented MLDSA keys, I'd assume Ed25519 won't be implemented (although I'd love to wrong, I'd definitely add support if the SEP does).